According to known art, loading machines for cartridges with a metal case substantially comprise a frame structure, feed means for metal cases, for ogival balls and for gunpowder, an operating beam supporting accessory means for in-line loading and processing of said cartridges, feed and conveying means of the cartridges during loading, and means for ejecting the loaded cartridges.
According to known art, the cartridge feed and conveying means generally comprise a race on which are the metal cases are positioned and slid, resting on their base with their open end pointing upwards, wherein the accessory loading means, or working tools, perform checking operations and introduce in sequence the various components that will go to make up and complete the finished cartridge.
Said cartridge feed and conveying means further comprise a conveyor guide, comb shaped and arranged parallel to said race, along its side turned towards the front of the machine and the operator, adapted to convey said cartridges along said race, to position them, according to the various filling steps, under the respective accessory loading means.
The main drawbacks of these loading machines for cartridges with metal cases concern the difficulty in keeping the cartridges perfectly coaxial with the respective filling means, during the various conveying and loading steps.
A non-perfect alignment between the axis of the cartridge, particularly of the metal case, and the vertical downward axis of the working tool risks ruining and damaging the case itself during filling, for example there may occur a lateral deformation of the case or its mouth may be crushed.
Similarly, there may disadvantageously be a deformation of the ball during its positioning on the case, or its positioning may be inclined with respect to the axis of the case, which could compromise the trajectory of the bullet when fired.
Further drawbacks relate to the long machine preparation times due to possible changes in the caliber of the cartridges being produced.
A single machine may in fact be used to produce cartridges of different calibers, and therefore, when passing from one caliber to another, the dimensions of the case race need to be varied with extreme precision, so as to keep the axis of the cartridge unchanged with respect to the working devices associated with the frame and to allow the correct operation of the machine and kinematic coordination of all moving parts.
In the traditional machine described above, in order to switch from the production of cartridges of a certain caliber to cartridges of another caliber, the operator has to manually perform the following operations:                moving the conveyor guide back, with respect to the cartridge race, by loosening the respective fixing means;        distributing the new-caliber cases along the race;        re-positioning the conveyor guide using measurement and alignment instruments adapted to ensure perfect parallelism and the correct distance between the race and the guide, in addition to trying to restore a condition of substantial coaxiality between the cartridge case and the working tools above;        stably fixing the guide to the moving parts, by re-positioning and tightening the respective fixing means.        
Disadvantageously, all these operations require a great deal of time, forcing the machine to be out of service for long periods, with consequent slow-down and reduction in productivity, causing economic losses.
Operators also need to use different instruments for measuring and checking the alignment and respect for the correct distance between the machine components, with obvious complications in terms of tuning and registry before the re-start of work.